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LGE Internal Use Only
Copyright © 2009 LG Electronics. Inc. All right reserved.
Only for training and service purposes
3. TECHNICAL BRIEF
LGE Internal Use Only
The current level magnitude is controlled by AnalogicTech’s Simple Serial Control(S
2
C wire) Serial
interface. The interface records rising edges of the EN/SET pin and decodes them into 16 different states.
The 16 current level setting available are indicated table in below.
Figure 3-6-3 AAT3157 current level setting
The AAT3157 is a low noise, constant frequency charge pump DC/DC converter that uses a tri-mode
load switch (1X), fractional (1.5X), and doubling (2X) conversion to maximize efficiency for white LED
applications. The AAT3157 is capable of driving six LEDs for a total of 180mA from a 2.7V to 5.5V input.
The current sinks may be operated individually or in parallel for driving higher current LEDs. A low
external parts count (two 1μF flying capacitors and two small 1μF capacitors at IN and OUTCP) make this
part ideally suited for small, battery-powered applications.
AnalogicTech's AS2Cwire™ (Advanced Simple Serial Control™) serial digital input is used to enable,
disable, and set current for each LED with a 16 setting down to 50 μA. The low- current mode supply
current can be as low as 50 μA to save power.
Each output of the AAT3157 is equipped with built in protection for output short-circuit and auto-
disable for load short-circuit conditions. Built-in softstart circuitry prevents excessive inrush current
during start-up. A low-current shutdown feature disconnects the load from the input and reduces
quiescent current to less than 1μA. The AAT3157 is available in a Pb-free, space-saving 2.85x3.0mm 12-
pin TSOPJW package.